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Invited speakers

• Temperature as a First-Class Citizen in Chip Design
  Sachin S. Sapatnekar, University of Minnesota, USA

Abstract: With new technology trends, arising through a confluence of factors such as Moore's law scaling and 3D integration, the role of thermal design is inexorably shifting from package-centric issues towards on-chip optimizations. This talk overviews the roots of this change, the circuit effects of elevated temperatures, and on-chip optimizations for effective thermal management.

• Boiling Heat Transfer and Flow Regimes in Microchannels - a Comprehensive Understanding
  Suresh V. Garimella, Purdue University, West Lafayette, USA

Although flow boiling in microscale passages has received much research attention over the last decade, the implementation of microchannel heat sinks operating in the two-phase regime has lagged due to the complexity of boiling phenomena at the microscale. The influence of a number of the governing parameters, such as microchannel geometry, mass flux, heat flux, vapor quality and fluid properties, on flow boiling heat transfer has not been clearly elucidated. In addition, issues such as flow instability, flow reversal, and large pressure drops appear to confound practical implementation. Also, despite the large number of empirical correlations that have been proposed in the literature for prediction of boiling heat transfer and pressure drop in microchannels, accurate design criteria for microchannel heat sinks are as yet unavailable due to the limited applicability of these correlations over a wide range of experimental conditions.

From extensive experimental work and analysis conducted in recent years in the authors’ group, a clear picture has emerged that promises to enable prediction of flow boiling heat transfer over a wide parameter space. Experiments have been conducted to determine the effects of important geometric parameters such as channel width, depth, and cross-sectional area, operating conditions such as mass flux, heat flux and vapor quality, as well as fluid properties, on flow regimes, pressure drop and heat transfer coefficients in microchannels. High-speed flow visualizations have led to a detailed mapping of flow regimes occurring under different conditions. Such a comprehensive flow regime map is facilitating the development of flow regime-based models for prediction of boiling heat transfer coefficients. In addition, quantitative criteria for the transition between macro- and micro-scale boiling behavior have been identified. Nondimensional parameters influencing the occurrence and extent of flow confinement are proposed. Issues such as flow instability and flow reversal, as well as the mitigation of these issues, are discussed.